This application relates to an arrangement of gas turbine engines in a wide fuselage aircraft to selectively bypass boundary layer air around the engines.
Gas turbine engines are known and typically include a fan delivering air into a compressor section. The air is compressed and delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
One potential application for gas turbine engines is in next generation aircraft with boundary layer ingestion into the propulsion system. One future aircraft has a wide fuselage. The aircraft is to be driven by twin gas turbine engines mounted in the tail section. The engines extend vertically upwardly above the fuselage.
The wide fuselage will create a large boundary layer of the air approaching the engines. Ingestion of the fuselage boundary layer enables an increase in the engine propulsive efficiency for improved fuel burn performance, but also raises challenges for the engine operation and, in particular, for the fan rotor.
As known, an aircraft experiences a number of different conditions during a typical flight cycle. The boundary layer may be ingested adequately by the engine during numerous operational conditions where the fan speed and inlet airflow are relatively high, such as takeoff or climb.
However, at the top of descent, a pilot will typically pull back the throttle, slowing the fan speed and reducing the inlet airflow. At the same time, the aircraft may still be at a relatively high velocity. Under such conditions, the boundary layer could become problematic with respect to engine operability or fan blade stress.